1. Field of the Invention
The present invention generally relates to an adaptive rubber insert that allows standard coaxial cable support products to be used to support fiber optic cable, power cable and hybrid cables.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
The following description of the art related to the present invention refers to a number of publications and references. Discussion of such publications herein is given to provide a more complete background of the principles related to the present invention and is not to be construed as an admission that such publications are necessarily prior art for patentability determination purposes.
For many years, coaxial cable was the standard type of cable used in the telecommunications industry to transmit a signal from a radio located on the ground to an antenna located on an elevated support structure. Due to advances in technology, the use of coaxial cable to transmit signals has become less common. The use of fiber optic cable to transmit the signal from the radio to the antenna has become the industry standard.
In addition to the coaxial or fiber optic cables, antennas often require a source of electrical power, which requires running a power cable from the power source on the ground up to the antennae on the support structure. In some cases, hybrid cables that carry both fiber optic and power cables are used to consolidate the number of cables required for a functioning antenna assembly. Whether or not hybrid cables are used, a multiplicity of cables run from the ground to the antenna at a base station.
Transmission line hangers are the preferred devices used for supporting coaxial cable and other types of cable in the telecommunications industry. They provide a means of securing the cable to a support structure. Hangers are typically made of metal or plastic. The hangers have been designed to support the common sizes of cable used in the telecommunications industry. Cable sizes include but are not limited to ⅜″, ½″, ⅞″, 1¼″, 1⅝″ and 2¼″ diameter cables. Typically, a different size of hanger is required for each size of cable. Hangers that have been designed to support coaxial cable are often not compatible with fiber optic cable, power cables or hybrid cables.
In order to limit the cost of retrofitting base stations with fiber optic cable, rubber hanger inserts or barrel cushions have been adapted to allow pre-existing hanger designs to be used for cables with different cross-sectional shapes and diameters. The hanger insert can be used without completely redesigning the traditional hangers used to support coaxial cable.
Hanger inserts are typically manufactured from UV-resistant EPDM (ethylene propylene diene monomer) rubber. Durometer is the international standard for hardness of rubber, and is measured on three different Shore Hardness Scales. Soft rubbers, including EPDM rubbers, are generally measured on the Shore A Scale. The standard hardness of prior art inserts is typically in the range of Shore 55A-60A, which is equivalent to tire rubber.
The commercially available inserts of the prior art are cylindrical and have a round, smooth hole through the center of the cylinder that envelops the cable when assembled. The inserts have an outer diameter that is matched to the size of the hanger, and an inner diameter that is particular to a specific diameter, cross-sectional shape, and type of cable. Some inserts are designed to support multiple small diameter cables, each in its individual opening. Inserts also have a lengthwise slit or other opening through which the cable can pass at the time of installation.
In order to assemble a standard line hanger with an insert, the insert is opened along the lengthwise slit, the cable is inserted through the slit into the opening in the center of the insert, and the insert is placed into the metal portion of the hanger. The hanger is then secured to the support structure of the antenna. Once the hanger is fully assembled, the hanger exerts pressure over the insert that hold it shut and immobile inside the hanger, resulting in a secure suspension system for the cable.